The present invention generally relates to improved lithography processing. In particular, the present invention relates to reducing resist debris on semiconductor substrates using ozone.
Microlithography processes for making miniaturized electronic components, such as in the fabrication of computer chips and integrated circuits, are of increasing importance as the trend towards miniaturization and integration continues. Lithography involves the use of resists to temporarily mask a semiconductor substrate surface to enable site specific additive, subtractive, or enhancing processing (e.g., deposition, etching, doping). Lithography specifically involves applying a coating or film of a resist to a substrate material, such as a silicon wafer used for making integrated circuits. The substrate may contain any number of layers or devices thereon.
The resist coated substrate is baked to evaporate any solvent in the resist composition and to fix the resist coating onto the substrate. The baked coated surface of the substrate is next subjected to selective radiation; that is, an image-wise exposure to radiation. This radiation exposure causes a chemical transformation in the exposed areas of the resist coated surface. Types of radiation commonly used in microlithographic processes include visible light, ultraviolet (UV) light and electron beam radiant energy. After selective exposure, the resist coated substrate is treated with a developer solution to dissolve and remove either the radiation-exposed or the unexposed areas of the resist (depending upon whether a positive resist or a negative resist is utilized) resulting in a patterned or developed resist. Many developer solutions contain water and a base, such as water and a hydroxide compound.
Treating a selectively exposed resist with a developer conventionally involves depositing the liquid developer solution over the resist clad substrate and spinning the substrate whereby the liquid developer solution and dissolved areas of the resist are removed from the substrate by centrifugal forces. A rinsing solution, typically deionized water, is then deposited over the resist clad substrate and the substrate is spun again to remove the water and any debris solubilized by the water. Spinning the substrate is a convenient and inexpensive method of removing materials from substrate.
The patterned resist covered substrate is then subject to standard semiconductor processing such as material deposition, etching, or doping. Since the patterned resist only covers a portion of the substrate, the standard semiconductor processing techniques impact desired areas of the substrate. This is the basis for fabricating integrated circuit chips.
After standard semiconductor processing (material deposition, etching, or doping) is completed, the patterned resist is removed or stripped from the substrate. This process is repeated numerous times until a desired product is obtained. However, it is important to completely remove the patterned resist from the substrate in order to prevent defects in the desired product (that is, deleteriously affect subsequent processing).
On one hand, there is a desire for a stripper to completely remove a patterned resist after standard semiconductor processing. Although it is difficult if not impossible to completely remove a patterned resist from a substrate, efforts in this direction involve the use of aggressive strippers. On the other hand, there is a desire for a stripper not to damage the underlying substrate while removing the patterned resist. Efforts in this direction involve using strippers that require undesirably long processing times. One problem associated with lithography, therefore, is using a stripper that completely removes a patterned resist without damaging the underlying substrate in a reasonable period of time. Such a stripper is presently desired. In lieu of such a stripper, alternative methods may be employed.
The present invention provides an improved cleaning process in connection with lithography. The present invention also provides methods for minimizing the presence of resist debris on resist developed and stripped semiconductor substrates. As a result of the present invention, post-lithography semiconductor processing is substantially improved.
In one embodiment, the present invention relates to a method of processing a semiconductor structure, involving the steps of providing the semiconductor structure having a patterned resist thereon; stripping the patterned resist from the semiconductor structure, wherein an amount of carbon containing resist debris remain on the semiconductor structure; and contacting the semiconductor structure with ozone thereby reducing the amount of carbon containing resist debris thereon.
In another embodiment, the present invention relates to a method of reducing carbon containing resist debris on a patterned resist stripped semiconductor structure, involving the steps of providing a semiconductor structure having a patterned resist thereon, the patterned resist comprising a carbon containing material; stripping the patterned resist from the semiconductor structure, wherein an amount of carbon containing resist debris remain on the semiconductor structure; contacting the patterned resist stripped semiconductor structure with at least one of a gas and a plasma comprising ozone and at least one inert gas thereby reducing the amount of carbon containing resist debris thereon; and rinsing the semiconductor structure.
In yet another embodiment, the present invention relates to a method of processing a semiconductor structure, involving the steps of providing the semiconductor structure having a patterned resist thereon, the patterned resist comprising a carbon containing material; stripping the patterned resist from the semiconductor structure, wherein an amount of carbon containing resist debris remain on the semiconductor structure; and contacting the semiconductor structure with at least one of a gas and a plasma consisting essentially of ozone and at least one inert gas selected from nitrogen, helium, and argon thereby reducing the amount of carbon containing resist debris thereon by at least about 90%.